Why it works: Pepper and lemon match in chemistry and in kitchens. They rank in the top 3% of all ingredient pairs, and cooks put them together in 27,047 recipes. Both carry trans-2-nonenal, which smells cardboard, fatty. The science ↓
Sauce Robert
Ingredients
Directions
Make the sauce
Melt the butter in a saucepan over medium heat.
Add the diced onions and fry until brown, but do not let them burn.
Stir in the flour and fry for another minute.
Add the gravy, salt, and pepper, and simmer gently for 10 minutes.
Skim the sauce to remove any impurities.
Remove from heat and stir in the mustard, vinegar, and lemon juice.
Serve
Serve the sauce around steaks or chops, garnished with fried parsley.
Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.
Explore the science
The flavor team
The pairs that carry this dish. Each one is judged two ways: how much their aromas overlap, and how often cooks already put them together.
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Pepper + lemontop 3% of all pairsSmell alikestrongCooked together27,047 recipes
Shared aroma: trans-2-nonenal (cardboard, fatty).
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Onion + mustardtop 6% of all pairsSmell alikestrongCooked together9,259 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Mustard + vinegartop 7% of all pairsSmell alikemoderateCooked together14,067 recipes
Shared aroma: isobutyraldehyde (malty, green).
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Pepper + mustardtop 9% of all pairsSmell alikemoderateCooked together15,430 recipes
Shared aroma: 2-isopropyl-3-methoxypyrazine (earthy, pea).
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Mustard + lemontop 11% of all pairsSmell alikestrongCooked together3,816 recipes
Shared aroma: eucalyptol (eucalyptus, herbal).
Ranks compare each pair with 20,000 random ingredient pairs on CompKitchen. How we score pairs
What each ingredient does
- Butter
- Provides fat for frying the onions and builds the base of the roux.
- Onions
- Browning them adds savoury depth and sweetness to the sauce.
- Flour
- Thickens the sauce when cooked briefly in fat to form a roux.
- Gravy
- Supplies the main liquid and meaty flavour of the sauce.
- Mustard
- Adds sharpness and a pungent flavour that cuts the richness.
- Vinegar
- Adds acidity that brightens the sauce and balances its richness.
The step that matters
Fry the onions until brown, not burnt. Browning builds savoury flavour through the Maillard reaction, but burnt onions turn bitter and spoil the whole sauce. Keep the heat moderate and watch closely.
Swap the onion
How well each one fits the dish's main ingredients (egg, butter, flour, pepper, mustard, vinegar, lemon):
- Shallotfits better
- Horseradishfits better
- Chivefits better
- Onionthe original
Fit is the average pairing score against egg, butter, flour, pepper, mustard, vinegar, lemon. Candidates are from the same food group and used in at least 100 recipes.
“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.
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